The present invention relates to a novel aqueous organopolysiloxane emulsion useful as an adjuvant in various kinds of hair-care treatment toiletry preparations, polishing compositions, mold-release agents, fabric-finishing agents and the like as well as to a method for the preparation thereof.
While various toiletry preparations or, in particular, hair-care treatment compositions are conventionally compounded with an aqueous emulsion of an organopolysiloxane or silicone, it is usual that the emulsion is an aqueous emulsion of an organopolysiloxane having a high viscosity in view of good slippery feeling and high combing smoothness imparted to the hair treated therewith. Such an aqueous emulsion of a high-viscosity organopolysiloxane is prepared usually by using an anionic or non-ionic surface active agent when the intended application of the emulsion is an adjuvant to a shampoo composition. Japanese Patent Kokai 4-36226 and 4-243813 disclose a shampoo composition formulated with an aqueous emulsion of an organopolysiloxane, according to which a shampoo composition of excellent performance without a decrease in the foaming behavior can be obtained when the droplets of the organopolysiloxane dispersed in the aqueous medium have an average droplet diameter smaller than 2 xcexcm. Japanese Patent Kokai 63-130512 and 5-163122 propose admixture of an aqueous emulsion of an organopolysiloxane in the form of a so-called microemulsion to a toiletry preparation. Further, Japanese Patent Kokai 7-188557 proposes use of an organopolysiloxane emulsion of which the dispersed droplets have a relatively large droplet diameter of 3 to 100 xcexcm in view of the problem that an organopolysiloxane emulsion on the hair is readily washed away from the hair due to poor adhesion when the droplet diameter is relatively small as in the microemulsion mentioned above. The adhesion of an organopolysiloxane emulsion to the hair, however, can be further improved only when the droplet diameter of the organopolysiloxane is increased so much. On the other hand, it is accepted as desirable that an organopolysiloxane emulsion is prepared by using a cationic or non-ionic surface active agent when it is to be used as an adjuvant to a cationic hair-care treatment composition such as hair rinses, hair conditioners, hair treatment agents and the like.
Along with this line, Japanese Patent Kokai 9-316331 and 11-148010 propose an organopolysiloxane emulsion prepared by using a cationic surface active agent having an alkyl group of 16 or 18 carbon atoms, respectively. The organopolysiloxane droplets as the dispersed phase in these aqueous emulsions, however, have a droplet diameter of 10 to 30 xcexcm. When the droplet diameter exceeds this range, the aqueous emulsion disadvantageously suffers a decrease in the storage stability because the emulsion is destroyed during storage. In addition, the content of the organopolysiloxane in these aqueous emulsions cannot exceed a range of 70 to 75% by because, when the content of the organopolysiloxane is larger than 75% by weight, the flowability of the aqueous emulsion is poor to cause inconvenience in handling.
Since an organopolysiloxane is in general a material having very low emulsifiability, an aqueous emulsion of an organopolysiloxane can usually be prepared only by giving a large quantity of mechanical energy using an emulsifying machine such as colloid mills, homogenizers, homomixers and the like. On the other hand, Japanese Patent Publication 4-49581 proposes a method for emulsification of an organopolysiloxane without using the above mentioned high-power emulsifying machines. This method, however, is a method for obtaining an aqueous emulsion of an organopolysiloxane having a relatively small droplet diameter with which combined use of a polyhydric alcohol is indispensable for emulsification. When the organopolysiloxane has a high viscosity, in particular, the above mentioned emulsifying machines are still insufficient for accomplishing full emulsification of such a high-viscosity organopolysiloxane so that proposals are made in Japanese Patent Kokai 7-173294 and 8-198969 on a method for the emulsification of a high-viscosity organopolysiloxane by using a special emulsifying machine capable of giving a high shearing force.
It is understood that, when a hair-care toiletry preparation is admixed with an aqueous emulsion of an organopolysiloxane, good improvements can be obtained in the deposition behavior of the organopolysiloxane to the hair and touch feeling and combing smoothness of the treated hair when the droplet diameter of the emulsified organopolysiloxane is relatively large. Further, the amount of the emulsion can be decreased with good handleableness when the concentration of the organopolysiloxane is high and the viscosity of the emulsion is low still with good storage stability of the emulsion. Further, it is desired to develop a method for efficiently emulsifying a high-viscosity organopolysiloxane by using a conventional general purpose stirrer machine without necessitating a special high-power emulsifying machine mentioned above which is indispensable in the prior art.
The present invention accordingly has an object to provide an aqueous emulsion of an organopolysiloxane having good storage stability despite the relatively large average diameter of the emulsified organopolysiloxane droplets in the range from 0.1 to 1.0 mm as well as to provide a method for the preparation of such an improved organopolysiloxane emulsion.
Thus, the aqueous emulsion of an organopolysiloxane, in which the average diameter of the emulsified organopolysiloxane droplets is in the range from 0.1 to 1.0 mm, comprises:
(A) from 70 to 90% by weight of
(A-1) an organopolysiloxane having a viscosity of 1xc3x97105 mPaxc2x7s or higher at 25xc2x0 C. represented by the average unit formula R1aSiO(4-a)/2, in which R1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms and the subscript a is a positive number in the range from 1.8 to 2.2, or
(A-2) a mixture consisting of
(a) from 10 to 90% by weight of an organopolysiloxane having a viscosity of 1xc3x97106 mPaxc2x7s or higher at 25xc2x0 C. represented by the average unit formula R1aSiO(4-a)/2, in which R1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms and the subscript a is a positive number in the range from 1.8 to 2.2, and
(b) from 90 to 10% by weight of an organopolysiloxane having a viscosity in the range from 10 to 1000 mm2/s at 25xc2x0 C. represented by the average unit formula R1aSiO(4-a)/2, in which R1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms and the subscript a is a positive number in the range from 1.8 to 2.2 or a hydrocarbon solvent having a boiling point in the range from 60 to 260xc2x0 C.;
(B) from 1 to 15% by weight of a surface active agent selected from the group consisting of cationic surface active agents represented by the general formula R24N+xc2x7Xxe2x88x92, in which at least one of the four R2 groups is an alkyl or alkenyl group having 12 to 22 carbon atoms, the rest of R2 groups, if any, being an alkyl group having 1 to 5 carbon atoms or a benzyl group, and Xxe2x88x92 is a halogen ion or an organic anion, anionic surface active agents and non-ionic surface active agents; and
(C) from 5 to 25% by weight of water as a solvent or dispersion medium of the components (A) and (B).